`cache_nils` is `true` by default

[jshoung]

@petergoldstein I'm not sure what I'm missing but the default behavior for caching nils we're experiencing in our Rails application is true even though the documentation says otherwise:

When I look at the code, it seems like the default is true as well:

dalli/lib/dalli/client.rb

Line 355 in 1d4cbfc

CACHE_NILS = { cache_nils: true }.freeze

dalli/lib/dalli/client.rb

Line 138 in 1d4cbfc

req_options = req_options.nil? ? CACHE_NILS : req_options.merge(CACHE_NILS) if cache_nils

[olleolleolle]

Ah, I think the code behaves like it should.

The suffix if controls the whole line 138. The whole line 138 does not get executed if the cache_nils method returns false.

[petergoldstein]

After investigation, the code and documentation are consistent: cache_nils defaults to false.

Looking at the implementation:

• Documentation (lib/dalli/client.rb:41): # - :cache_nils - defaults to false
• The cache_nils method returns @options[:cache_nils], which is nil (falsy) when not set
• The protocol layer converts this to a boolean: opts[:cache_nils] ? true : false

So when cache_nils is not explicitly set, it evaluates to false, meaning nil values are not cached by default.

If you're seeing different behavior in your Rails application, it may be due to:

1. Rails' ActiveSupport::Cache::MemCacheStore setting its own defaults
2. A configuration somewhere in your app explicitly setting cache_nils: true

You can verify the actual option value with:

client = Dalli::Client.new('localhost:11211')
puts client.instance_variable_get(:@options)[:cache_nils].inspect  # => nil (falsy)

If you believe there's still an issue, please reopen with a minimal reproduction case.